Free Radical Scavenging and Tyrosinase Inhibition Activity of Aromatic Volatile Oil from Thai Medicinal Plants for Cosmetic Uses

Free radical scavenging and tyrosinase inhibition activity of thirteen aromatic oils from Thai medicinal plants were investigated. A stable free radical DPPH (1, 1-diphenyl-2-picryhydrazyl) was used in the free radical scavenging assay and mushroom tyrosinase enzyme was used in the tyrosinase inhibition test. The two assays were performed in 96-well plates and the absorbance measured by a well reader. Betel vine and holy basil oils gave the highest free radical scavenging activity with percent residual rate of absorbance (%RRA) of ≈ 15%, which is comparable to vitamin E and vitamin C, widely used in antiwrinkle cosmetics. Kaffir lime leaf and fruit peel oils showed the highest tyrosinase inhibition activity of ≈ 86.8 and 100%, respectively, which is similar in potency to kojic acid, a popular ingredient in whitening cosmetics. This study demonstrated the potential use of aromatic volatile oils extracted from Thai medicinal plants in commercial cosmetics. INTRODUCTION Recently natural plant extracts are being studied for use in cosmetics, since use of synthetic chemicals in cosmetics usually have inappropriate physical properties causing irritation and allergy to skin. Two main acclaimed activities of these extracts are antiaging and whitening effects. The mechanisms of these two activities are free radical scavenging and tyrosinase enzyme inhibition. Many natural compounds (vitamin E, vitamin C, carotenoids and plant phenolic compounds) extracted from plants have been successfully used in cosmetics (Haraguchi et al., 1995; Yoshino et al., 1994; Teguno et al., 1998; Yen et al., 2000; Pietta, 2000). Thailand has high plant biodiversity, and many Thai plants have been traditionally used in folk medicines, in foods as spices, in massage and in aromatherapy. Thailand imports many active chemicals including aromatic oils for use in cosmetics each year. In order to make use of its own natural resources, especially aromatic oils for cosmetic application, the activities of free radical scavenging and tyrosinase inhibition activity of various aromatic volatile oils extracted from Thai medicinal plants were investigated. MATERIALS AND METHODS A total of 13 aromatic volatile oils from Thai medicinal plants were obtained from Thai-China Flavors and Fragrances Industry Co., Ltd. (TCFF, Ayudthaya, Thailand). These oils were from holy basil (Ocimum sanctum, Linn), sweet basil (Ocimum basilicum, Linn), tumeric (Curcuma longa, L.), lesser galanga (Alpinia officinarum), betel vine (Piper betel, Linn), lemon grass (Cymbopogon citratus, Stapf), citronella (Cymbopogon nardus, Rendle), plai (Zingiber montanum), vetiver (Vetiveria zizanioides), lavender (Lavandula angustifola, P.), Kaffir lime leaf (Citrus hystrix, DC), Kaffir lime fruit peel (Citrus hystrix, DC) and black pepper (Piper nigrum, L.). They were tested for free radical scavenging activity using an electrochemical method (Yamasaki et al., 1994), and tyrosinase inhibition assay (Matsuda et al., 1996). In the free radical scavenging assay system, acetate buffer (pH 5.5, 80 μl), Proc. WOCMAP III, Vol.6: Traditional Medicine & Nutraceuticals Eds. U.R. Palaniswamy, L.E. Craker and Z.E. Gardner Acta Hort. 680, ISHS 2005 98 absolute alcohol (50 μl), a stable free radical DPPH (1,1-diphenyl-2-picrylhydrazyl, 100 μL 2.53 x 10 M, Sigma Co., St. Louis, Missouri) and 40-80 μL 0.5% oil samples or standards (vitamin E or vitamin C, Sigma Co.) were mixed in 96-well plates and the absorbance at 570nm were kinetically determined by a well reader (Seikagaku Corporation, Tokyo, Japan) at 30 seconds, 1, 2, 3, 5, 10, 17 and 21 min. The time that gave maximum absorbance in all samples was selected. The % RRA (residual rate of absorbance) of each oil sample was calculated from the maximum O.D. compared to control according to the equation: